Wearable fitness monitors and trackers are commonly implemented in a wristband-type form factor so that they may be worn as a watch. Such wearable fitness monitors commonly have a fitness monitor or tracker body to which wrist straps (also referred to herein as wrist band portions or strap portions) are attached. Such straps may be fastened to one another, for example, using a standard buckle-and-tang clasp, a snap-clasp, or other fastening system. In most such scenarios, one strap portion, which is referred to as the “buckle” portion or strap herein (even if it uses a fastening mechanism other than a buckle), has a mechanism attached to one end, and the other strap portion, which may be referred to as the “adjustment” portion or strap, has features that allow the adjustment portion or strap to be variably located relative to the buckle portion or strap and then secured relative to the buckle portion or strap by the fastening mechanism.
A snap-clasp, such as the snap-clasps used in the Nike+SportBand™, fastening system, includes an adjustment portion or strap that has a series of through-holes in it, and a buckle portion or strap that has one or more posts protruding from it that may snap into one or more of the holes on the adjustment portion or strap. Such clasps are attractive from a manufacturing perspective, as only one separate piece (a peg component with the post or posts) must be made, although the adjustment portion or strap will frequently require reinforcement with a spine of stronger material than the material from which the rest of the adjustment portion is made—this is because the soft elastomeric materials commonly used for wristbands may not be rugged enough to withstand repeated insertion/removal of the posts, and may also not be strong enough to retain the posts if the wristband snags on an object. The snap-clasp has a low profile since the peg component may be flush with the exterior surface of the buckle portion or strap, which reduces the chances of a snap-clasp band scratching or catching on objects. Snap clasps, however, may be difficult to fasten snugly onto a person's wrist since the person must frequently squeeze the end of the buckle portion or strap with the posts, as well as the portion of the adjustment portion or strap having the holes into which the posts are being inserted, in between two fingers in order to push the posts into the holes. This means that the wristband is sized to accommodate the person's wrist+one finger, and once the finger is removed, the wristband may be loose, which can interfere with heart rate measurement (which commonly requires good skin-to-device contact). Snap-clasps may also, despite the reduced chance of them snagging on objects, catch on edges or other obstacles, causing them to unfasten—if this is not noticed by the wearer, it can result in the unit being lost.
Buckle-and-tang clasps, which are frequently used in watches, feature a buckle, a tang, a pivot bar, and a keeper, in addition to the buckle strap and the adjustment strap. The buckle and the tang are both affixed to the buckle strap by way of the pivot bar, allowing both components to rotate freely with respect to one another and the buckle strap. The tang is long enough that it cannot rotate past the buckle, and, during use, is threaded through holes in the adjustment portion or strap, thereby preventing the adjustment portion or strap from being pulled through the buckle. Buckle-and-tang clasps are extremely secure, but are more expensive to manufacture than snap-clasps due to the increased part count and assembly complexity of the buckle-and-tang assembly.
Discussed herein is a new fastener system for watches, fitness trackers, and other devices that may be worn on a person's limbs.